The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.
Technologies for compressing video data include H.261, H.263, H.264, MPEG-2, MPEG-4, and so on. According to such video compression standards, each image is split and encoded into fixedly sized macroblocks formed of rectangular areas having pixels sized 16×16 of luma component and pixels sized 8×8 of chroma component. All luma components and all chroma components of each macroblock are spatially or temporally predicted, and then a predicted residual undergoes a transform, a quantization, and an entropy coding and finally a transmission. The most recently enacted H.264/AVC standard prescribes an encoding apparatus to use a 16×16 pixel block for the fixed macroblock size and subdivide each macroblock into smaller blocks for which an intra prediction or an inter prediction is carried out. In carrying out the intra predictive encoding, each macroblock may be split into 16×16, 8×8, or 4×4 pixel sizes, and the block of pixel size 16×16 is intra-predicted in one of four prediction modes, 8×8 and 4×4 blocks are intra-predicted in one of nine prediction modes. In the case of inter prediction, the macroblock may be subsplit into blocks of pixel sizes 16×16, 16×8, 8×16, 8×8, 8×4, 4×8, or 4×4, and then used for the inter prediction through a motion compensation. The transform is performed by unit of 8×8 or 4×4 pixel sized blocks, and the quantization used for the transform coefficients is scalar quantization.
However, the inventor(s) has noted that the 16×16 macroblock is considered appropriate for small images by the class of the known QCIF (Quarter Common Intermediate Format) and CIF (Common Intermediate Format) and it is not the right macroblock size for compressing a high resolution image such as a 4K×2K image. In addition, the inventor(s) has noted that since typical video compression technology uses a fixedly sized macroblock in encoding an image (even though H.264/AVC subdivides and encodes macroblock into smaller block units, the macroblock is of a fixed size), encoding the high resolution image hardly achieves a sufficient encoding efficiency.